A study was made of O mobility by using internal friction measurements. Two energy dissipation peaks, which were closely related to the O concentration, were observed at 115K (kHz frequencies) and 510K (low frequencies). Both of these were relaxation peaks. The first, at low temperatures, had an activation energy of 0.17eV. The second, at high temperatures, had an activation energy of 1.10eV. Both had associated frequency factors which were of the order of 1012/s. Vacuum annealing showed that the heights of both peaks decreased continuously as the annealing temperature was increased. The relaxation strength reduction during annealing was compared with gravimetric O loss, electrical resistivity, and X-ray diffraction measurements. The peak relaxation strengths were closely related to the O loss. Two relaxation models, both based upon O movement within the basal Cu-O plane, were suggested to explain these 2 internal friction peaks.

Y.Mi, D.Mari, R.Schaller, W.Benoit: Materials Science Forum, 1993, 119-121, 707-12